* Ipc$ Share

[Nicodemo Aidara]

TheIPC$ is a hidden share maintained by the Server service (Disabling the service will remove the share). The IPC$ share is used for Inter Proces Communication by using RPC (Remote Procedure Call), allowing the client to send different commands to the server

I know it's been a while since the original post, but I was also searching for a permanent solution to remove IPC$ folder which will insistently be back every time you reboot your machine or restart the server service.

So I decided to create my own solution which removes the IPC$ admin shared folder every time I boot my computer. This also avoid the amount of issues caused for disabling the Server service. And because the Server service won't be disabled, you can also continue sharing other folders and a printer for example.

The IPC$ share is also known as a null session connection. By using this session, Windows lets anonymous users perform certain activities, such as enumerating the names of domain accounts and network shares.

The IPC$ share is created by the Windows Server service. This special share exists to allow for subsequent named pipe connections to the server. The server's named pipes are created by built-in operating system components and by any applications or services that are installed on the system. When the named pipe is being created, the process specifies the security associated with the pipe. Then it makes sure that access is only granted to the specified users or groups.

However, an administrator has controls over any named pipes that were enabled. They can be accessed anonymously by using the Network access: Named Pipes that can be accessed anonymously security policy setting. If the policy setting is configured to have no entries, such as a Null value, no named pipes can be accessed anonymously. And you must ensure that no applications or services in the environment rely on anonymous access to any named pipes on the server.

In Windows Server 2012 or a later version, there's a feature to determine whether anonymous sessions should be enabled on file servers. It's determined by checking if any pipes or shares are marked for remote access.

The IPC$ is a hidden share maintained by the Server service (Disabling the service will remove the share). The IPC$ share is used for Inter Proces Communication by using RPC (Remote Procedure Call), allowing the client to send different commands to the server:

Certain commands can be accessed anonymously through a NULL session depending on the configuration of the server. If the command cannot be called anonymously, then the client has to authenticate. Access is granted if the client can provide proper credentials (username and password), that matches an account on the server. If not able to do this, then the user at the client machine will get an error like:

Note it is possible to access the IPC$ share of a server by using a different credentials, than those used when logging on the client machine. (Even if needing to use a domain-user to access a server from outside the domain).

SysAdmins use the ADMIN$ share for programs and services to deploy or run from a network, remotely. The IPC$ share is the default share you connect to when you type \\hostname in your address bar. These shares are required for SysAdmins to deploy their software or otherwise manage their environment of Windows clients.

By default, Windows automatically creates special hidden administrative shares that administrators, programs, and services can use to manage the computer environment or network. These special shared resources are not visible in Windows Explorer or in My Computer.

I went to Control Panel -> Network and Sharing Center -> Change Adapter Settings, right-clicked on the LAN connection, and clicked Properties. I found that many services and clients were not installed on the network adapter, at all! It had IPv4 installed, and that was it! I had to add more to the list.

This can be daunting to touch every computer, and navigate a likely-customized Control Panel. If you want to do it via the command line, check out this post for adding the protocols, services and client with the command line. Save it as a .CMD file, then you can run around with a USB stick or stick it on a network server.

I must say, without a doubt, that Digital Ocean is one of the best companies available for hosting services. This is not a sales pitch, but an actual account of what has happened since I joined them over a year ago.

The IPC$ share is used with temporary connections between clients and servers by using named pipes for communication among network programs. It is primarily used for to remotely administer network servers.

I can access the data shares on this server without problem from any Unix based computer with mount.cifs. However, when I try to access them from Windows computers (tested with Windows 7 and 10), I get an Access denied error just after providing my credentials.

After recording the SMB traffic, I noticed that Windows computers always do a Tree connect request on the IPC$ share before trying to access the share I provided (through map network drive or add network location). My samba server returns Access denied for the IPC$ share and Windows never tries to access the share I want.

So my question is how can I prevent Windows to do this useless request on IPC$ and just access the share I provided? Or at least how can I force Windows to access the real share after the IPC$ one returned Access denied?

The answer is that you can't! Sorry to say, but this is the case. However, although this is the true answer to your question - I don't want to sound unhelpful. I do want to help, so hopefully what follows is the best advice I can give that will prove useful to you in your situation.

I am a professional penetration tester, and often use anonymous share access (such as IPC$) to obtain information about and break into systems for legitimate testing purposes. The key thing is to prevent enumeration of users and shares by an anonymous user (someone without valid credentials). Once valid credentials are obtained there are usually other ways of enumerating users (e.g. cat /etc/passwd), and it becomes less of a priority to an attacker anyway.

If you use this method, then clients will be given an `access denied'reply when they try to access the IPC$ share. Those clients will notbe able to browse shares and may also be unable to access some otherresources. This is not recommended unless for some reason you cannotuse one of the other methods just discussed.

The reason why it is not recommended is because "Those clients... may also be unable to access some other resources." Windows not being able to access any shares on the machine is an example of this. Unfortunately Windows requires access to IPC$ in order to view the other shares. If it can't see IPC$ it just assumes that no other shares are available and gives up.

Linux client implementation of Samba works slightly differently and therefore doesn't experience the same problem. As there isn't a way round it, I would just ensure that the IPC$ share isn't giving away information to anonymous users.

Using the Host-based protection and User-based protection sections of the article you sent are good ways of preventing undesirable access to all of Samba, including the IPC$ share from untrusted sources, and may well give you everything you need.

Computer Configuration\Windows Settings\Security Settings\Local Policies\Security Options\ Network access: Allow anonymous SID/Name translation = disabled Network access: Do not allow anonymous enumeration of SAM accounts =enabled Network access: Do not allow anonymous enumeration of SAM accounts and shares =enabled Network access: Let Everyone permissions apply to anonymous users=disabled Network access: Named Pipes that can be accessed anonymously= Network access: Shares that can be accessed anonymously=

and that anonymous enumeration(shares, users, etc..) does not work, but I've been told that if the above command completes successfully then the risk remains and we need to correct it. I'm at a loss as to what other settings would fix this and do not want to script the deletion of the share. Are there any other settings that need to be set? Should these setting cause the anonymous connection to fail? Is there anything else I might have missed?

Check the latest guidance in the SCM for your OS. According to the baseline for 2k8r2 SP2, restrict anonymous access to named pipes and share should be enabled. You should be setting this via group policy, and should probably audit your security baseline with the tool as well.

The IPC$ share is also known as a null session connection. By usingthis session, Windows lets anonymous users perform certain activities,such as enumerating the names of domain accounts and network shares.

The IPC$ share is created by the Windows Server service. This specialshare exists to allow for subsequent named pipe connections to theserver. The server's named pipes are created by built-in operatingsystem components and by any applications or services that areinstalled on the system. When the named pipe is being created, theprocess specifies the security that is associated with the pipe, andthen makes sure that access is only granted to the specified users orgroups.

one would think that when it asks for a password that you can use the password from a user on the w2kpro system to gain printer access. But if it does not have drivers loaded, you still may not be able to print from the 98 box.

If it still wont share try restarting the server service.

here is a differnet idea.

share a directory on the win2k por machine for the win98 machine. They can copy the file to that directory. Here is the tricky part. You need to have a program look for a file in that directory then print it.

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